A plastic surgeon, with an particular expertise in women's behinds, has devised the definitive guide to bottom shape. According to Dr Matthew Schulman, from New York, all women's behinds on the planet fall into one of five categories - square, V-shape, A-shape, round or upside-down heart.
If you're a little on the larger side, Dr Schulman recommends a big pair of knickers that covers most of the bum, as this can give your derriere maximum coverage.
"When you've got a round bottom, it's good to go for a style that doesn't "cut" your silhouette in two," Elise explains. "You want support but it's also good to reveal a bit of your bottom."
Pear-shaped women are likely to have A-shape bums and, says Dr Schulman, they should go for larger leg holes to accommodate their fuller thighs.
"You'll definitely want larger leg holes - and low-waist, hipster knickers will enhance your shape too," Elise adds. 'The idea is to have a hip-revealing shape that will really emphasise the under-bum part.'
An 'upside-down heart' shape is a round, pert derriere with extra volume around the lower part of the hip.
"If you're lucky enough to have a heart-shaped bum and a skimpy waist, you could wear almost any knickers," Elise explains.
"Midi-briefs look particularly nice on this body shape as they're not too high, but they're narrower at the side, which shows off a shapely bum.
"Briefs are back on-trend - even in swimwear - as they flatter your narrow waist and make your thighs look longer, which in turn makes you appear taller. They'll also show off your bum nicely."
If your hip bone and outer thigh are perfectly in line, then you'll fall into the square category - and Dr Schulman recommends 'boy shorts' as they're less likely to ride up and give you a wedgie.
"These are perfect if you've got a flat bum, as shorts or boxer-style pants can add a bit more volume," Elise explains. "It's also great to pick a pair with a seam running up the middle with a bit of gathering; this will be more flattering visually than a flat piece of fabric as it gives shape.
"They'll also sit nice and flat on the body; you won't have the problem of the leg line rising up."
Women with narrow hips and broad shoulders are most likely to boast a V-shape bum, with the line beween your hips and pelvis angling inward - best enhanced with a classic pair of briefs that cups the bottom of your buttocks, according to Dr Schulman.
"For this body shape, a slightly higher leg is flattering," Elise says. 'It emphasises the waist nicely and flatters the silhouette.
"We're seeing more and more styles like this with lace inserts - gone are the days of giant Bridget Jones knickers! This shape will also makes the legs look longer whilst showing off your curves; it really emphasises the hourglass figure.